The present invention relates to a lockable joint for articulated members and more particularly to a joint locked in axial alignment by engagement of complimentary nesting surfaces on the members.
A search of the prior art failed to uncover any patents which disclosed the lockable joint of the present invention. A number of patents were uncovered which disclose various devices for locking or latching articulated members relative to one another. The following is a listing of such patents uncovered during the aforementioned prior art search:
U.S. Pat. No. 553,650; U.S. Pat. No. 788,223; U.S. Pat. No. 875,195; U.S. Pat. No. 1,668,290; U.S. Pat. No. 2,466,205; U.S. Pat. No. 2,690,369; U.S. Pat. No. 3,547,054.
U.S. Pat. No. 553,650 to Kingsland discloses a lock chain device particularly for use in flue-cleaning apparatus and comprises a plurality of elongated links pivotally connected in end-to-end relation. The end of one link is provided with a pin and an irregular recess which receives respectively a longitudinal slot and a projection having a shape corresponding to the irregular recess such that, when axially aligned, the confronting link ends may be thrust together. Locking of the links together, therefore, requires that external rotational forces be applied to longitudinally align the links prior to urging them into locking engagement.
U.S. Pat. No. 788,223 to Simpson and U.S. Pat. No. 1,668,290 to Stevens each disclose a foldable carpenter's square. The square devices disclosed in these patents comprise two limbs pivotally connected together by a pin and an elongate slot so that the limbs may be pivoted either to a parallel folded position for ease of transportation or to a right-angled position for use as a carpenter's square. The pivotally connected ends of the limbs are provided with complementary mating surfaces which lockably engage only when the limbs are positioned at right angles to each other and urged together.
U.S. Pat. No. 875,195 to Loftin, U.S. Pat. No. 2,466,205 to Burr and U.S. Pat. No. 2,690,369 to Laskey et al. all disclose folding tables having legs pivotable between a collapsed position parallel to the table surface and an erected position normal to the table surface. The legs of the tables of each of these patents are pivotally connected at the table corners by means of pins, bolts or studs engaging in L-shaped slots or apertures. Cooperating elements on both the table top and legs are provided for latching the legs in their erected positions. In the case of each of these prior art devices, the legs are manually articulated into positions with the matching elements in alignment and then urged into their latched positions.
U.S. Pat. No. 3,547,054 to Caldwell et al. discloses a folding telescopic support or leg which is resiliently biased for selectively and releasably securing the leg in a folded or erected position. The leg is pivotally connected to a support surface such as a table top by a pivot bearing received in a longitudinal slot in the upper end of the leg. Both the table top and leg are provided with coacting latch elements arranged on opposite sides of the pivot bearing and which are resiliently biased into their latched position upon alignment of the latch elements.
It should be apparent, therefore, that, while the aforedescribed devices provide useful locking joints for relatively articulated members in certain applications, they fail to provide a mechanism by which angularly offset members are articulated into alignment and locked and vice versa by a rotational moment resulting from a force applied longitudinally to one or both of the members. Typically, the prior art devices are designed and constructed so that the articulated members and their latching elements must be in substantial alignment before they can be urged into their latched positions. In applications where precise initial alignment of the articulated member is not possible, desired, or economically feasible, such prior art mechanisms are unsuitable and would be subject to numerous malfunctions, such as jamming, binding and the like.